Visual function is mainly located within the bilateral hemisphere of the occipital lobes of the brain. However, our functional magnetoencephalography (MEG) result has demonstrated the reorganization of brain activity in the occipital area in patients with left-sided brain tumour. The results showed that brain laterality changes from bilateral to unilateral activation of the occipital area. Right occipital area (contralateral areas to the tumour), shows increase intensity of activation. Diffusion tensor imaging (DTI) with fibre tracking was performed to further investigate this brain laterality modification and the findings confirmed there is an alteration in the left hemisphere fibre optic tracts. This functional modification and changes of the brain laterality and optic tracts in the brain is suspected to be the result of tumour growth induced changes. The present observation will be discussed in term of the mechanism of tumour induced reorganization and changes with the corroborating evidence from MEG, DTI and neuropsychological assessment.
Proses penuaan seringkali dikaitkan dengan kemerosotan sistem kognitif. Kemerosotan tersebut bermula seawal usia dua puluhan dan berterusan secara linear. Walau bagaimanapun, kesan penuaan ke atas ciri kehubungan antara kawasan otak masih belum difahami. Dalam kajian ini, pengimejan resonans magnet kefungsian (fMRI) digunakan untuk mengkaji kesan penuaan ke atas kehubungan otak yang terhasil daripada tugasan mengulang secara terbalik (BRT). Subjek normal dalam empat kumpulan umur iaitu 20-29 tahun (n=14), 30-39 tahun (n=14), 40-49 tahun (n=10) dan 50-65 tahun (n=14) mengambil bahagian dalam kajian ini. Stimulus BRT terdiri daripada satu siri lima perkataan yang diberi secara auditori. Pemetaan statistik berparameter (SPM) dan pemodelan sebab dan akibat dinamik (DCM) digunakan untuk menentukan pengaktifan dan kehubungan otak. Sebanyak 200 model kehubungan intrahemisfera dan 150 interhemisfera dibina bagi menguji kewujudan gandingan antara girus temporal superior (STG), girus Heschl (HG), talamus (TH) dan girus presentral (PCG) kesemua subjek. Keputusan DCM menunjukkan subjek keempat-empat kumpulan umur menggunakan kehubungan intrahemisfera yang sama semasa tugasan BRT. Kehubungan interhemisfera pula didapati berubah menjadi semakin kompleks apabila usia meningkat. Perubahan tersebut didapati bermula pada usia 40 tahun. Keputusan ini menyokong penemuan terdahulu bahawa penuaan menyebabkan perubahan pada sistem neuron otak seterusnya mempengaruhi pemprosesan kognitif.
Neuroplasticity has been subjected to a great deal of research in the last century. Recently, significant emphasis has been
placed on the global effect of localized plastic changes throughout the central nervous system, and on how these changes
integrate in a pathological context. The present study aimed to demonstrate the functional cortical reorganization before
and after surgery using magnetoencephalography (MEG) in a participant with brain tumor. Results of Visual Evoked
Magnetic Field (VEF) based on functional MEG study revealed significantly different of MEG N100 waveforms before and
after surgery. Larger and additional new locations for visual activation areas after the surgery were found suggesting
neuroplasticity. The present study highlight a physiological plasticity in a teenage brain and the alterations regarding
neural plasticity and network remodeling described in pathological contexts in higher-order visual association areas.
The present study discussed functional reorganization and alteration in respond to the slow-growing tumour,
hemangiopericytoma in the occipital cortex. Visual evoked field (VEF) and auditory evoked field (AEF) using
magnetoencephalography (MEG) was used to evaluate the source localization and brain activity. Results of VEF source
localization show a typical brain waves. Brain activity of the occipital lobe demonstrate low activation in the ipsilateral
to the tumour. However, result shows the activation on the contralateral hemisphere was high and bigger in activation
volume. AEF result shows an identical source localization and both side of the temporal lobe are activated. This result
suggests that there is a positive plasticity in auditory cortex and slow-growing tumour can induce functional reorganization
and alteration to the brain.
Proses penuaan seringkali dikaitkan dengan kemerosotan pada sistem kognitif. Kemerosotan kognitif bermula seawal
usia dua puluhan dan berterusan secara linear. Selain itu, kemerosotan kognitif juga menjadi lebih nyata dengan
kehadiran hingar latar. Walau bagaimanapun, kesan penuaan ke atas mekanisme pemprosesan persepsi pertuturan
menggunakan tugasan mengulang secara terus (FRT) dalam senyap dan hingar belum difahami dengan jelas. Dalam
kajian ini, pengimejan resonans magnet kefungsian (fMRI) digunakan untuk membandingkan kesan penuaan ke atas
kehubungan efektif otak yang terhasil daripada tugasan FRT ke atas subjek normal dengan empat kumpulan umur yang
berlainan iaitu 20 - 29 tahun (n = 15), 30 - 39 tahun (n = 15), 40 - 49 tahun (n = 10) dan 50 - 65 tahun (n = 14). Satu siri
lima perkataan yang diselang-seli dalam keadaan hingar dengan senyap diberikan secara auditori. Pemetaan statistik
berparameter (SPM8) dan pemodelan dinamik penyebab (DCM10) digunakan untuk menentukan kehubungan efektif otak.
Kawasan yang terlibat dalam pembinaan model kehubungan efektif otak adalah STG, HG dan PCG. Model optimum yang
dipilih dalam kajian ini adalah model yang menunjukkan keseimbangan antara ketepatan dan kesukaran. Keputusan
fMRI kehubungan efektif menunjukkan bahawa komunikasi antara intrahemisfera tidak berubah dengan menggunakan
tugasan FRT ini apabila seseorang semakin berusia, tetapi komunikasi antara interhemisfera menjadi semakin kompleks.
This study investigated the functional specialisation characteristics of brain in multiple right-hand dominant subjects pertaining to the activation of the cerebral motor cortices evoked by unilateral finger tapping, especially in primary motor (M1) and supplementary motor (SMA) areas. This multiple-subject study used unilateral (UNIright and UNIleft) selfpaced tapping of hand fingers to activate the M1 and SMA. Brain activation characteristics were analysed using statistical parametric mapping (SPM). Activation for UNIright and UNIleft showed the involvement of contralateral and ipsilateral M1 and SMA. A larger activation area but with a lower percentage of signal change (PSC) were observed in the left M1 due to the control on UNIright (4164 voxels at a = 0.001, PSC = 1.650) as compared to the right M1 due to the control on UNIleft (2012 voxels at a = 0.001, PSC = 2.377). This is due to the influence of the tapping rate effects which is greater than what could be produced by the average effects of the dominant and sub-dominant hands. The significantly higher PSC value observed in the right M1 (p < 0.05) is due to a higher control demand used by the brain in coordinating the tapping of the sub-dominant fingers. The findings obtained from this study showed strong evidence of the existence of brain functional specialisation and could be used as baseline references in determining the most probable motor pathways in a sample of subjects.